1. Field of the Invention
The present invention relates to a photographic film cassette, a camera for use therewith, and a method of manufacturing the cassette. More particularly, the present invention relates to an improvement of a photographic film cassette, having a moveable closing structure, in which a leader of a photographic film can be advanced to the outside of a cassette shell when a spool is rotated in an unwinding direction, and a camera and a manufacture method associated with such a cassette.
2. Description of the Related Art
A known photographic film cassette includes a photographic film which is positioned so that a leader thereof does not protrude from the cassette shell prior to loading the cassette in a camera. A simple photographic film-transporting mechanism of the camera is typically used with this type of cassette, and includes a construction which rotates a spool to unwind a photographic film strip (hereinafter called as film), thereby causing the leader to move through a passageway formed in the cassette shell to an exterior of the cassette shell. Such a cassette is disclosed in U.S. Pat. Nos. 4,834,306 and 5,174,519. To prevent ambient light from entering the cassette shell, plush, or light-trapping ribbons, are conventionally attached to the inside of the passageway. U.S. Pat. No. 4,221,479 also discloses that a movable closing structure selectively encloses the inside of the cassette shell in a light-tight manner.
When a camera is loaded with the cassette, the closing structure is opened, by a mechanism in the camera, before the advancing mechanism incorporated in the camera rotates the spool in the unwinding direction to advance the leader. The closing structure is closed when the photographic film is wound back into the cassette shell after exposure of the photographic film is completed. Accordingly, the closing structure protects the exposed photographic film from being inadvertently subjected to ambient light. Use of the moveable closing structure instead of plush, is favorable, because less load is applied to the leader during advancement of the film. This facilitates the advancement of the film in response to rotation of the spool.
It is well known that the photographic film is constituted by applying photosensitive emulsion to one surface of a base, which is formed e.g. of cellulose triacetate (TAC). In the manufacturing process, the photographic film is dried after applying the coating of emulsion to the base. The photographic film shrinks, to degrees different between the emulsion surface and the back surface, during drying. In particular, as illustrated in FIG. 25, an emulsion surface 2a tends to shrink more than a back surface 2b, to cause a photographic film 2 to curl. When a spool 40a is rotated, a leader 2d of the photographic film 2 is exited through a passage mouth 5 from a cassette shell 40b, with a curled amount of W.
The photographic film cassette 40 in FIG. 25 incorporates a shutter member 194 as a moveable closing structure disposed at the passage mouth 5. Both surfaces 2a and 2b of the photographic film 2 come in direct contact with inside walls of the passage mouth 5 as the film 2 is advanced out of the cassette shell. The curling of the photographic film 2 causes the photographic film 2 to rub against the inside of the cassette shell 40b. Accordingly, the cassette shell 40b may damage the photographic film 2. Any scratches formed on the photographic film 2 are conspicuously enlarged on resulting photoprints. This lowers the quality of the photoprints.